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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on ErMnO3 by Materials Project

ErMnO3 crystallizes in the hexagonal P6_3cm space group. The structure is three-dimensional. there are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to seven O2- atoms to form distorted ErO7 pentagonal bipyramids that share corners with three equivalent MnO5 trigonal bipyramids, edges with six ErO7 pentagonal bipyramids, and edges with three equivalent MnO5 trigonal bipyramids. There are a spread of Er–O bond distances ranging from 2.27–2.41 Å. In the second Er3+ site, Er3+ is bonded to seven O2- atoms to form distorted ErO7 pentagonal bipyramids that share corners with three equivalent MnO5 trigonal bipyramids, edges with six equivalent ErO7 pentagonal bipyramids, and edges with three equivalent MnO5 trigonal bipyramids. There are a spread of Er–O bond distances ranging from 2.27–2.32 Å. Mn3+ is bonded to five O2- atoms to form MnO5 trigonal bipyramids that share corners with three ErO7 pentagonal bipyramids, corners with six equivalent MnO5 trigonal bipyramids, and edges with three ErO7 pentagonal bipyramids. There are a spread of Mn–O bond distances ranging from 1.91–2.08 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Er3+ and three equivalent Mn3+ atoms to form OErMn3 trigonal pyramids that share corners with six equivalent OEr3Mn tetrahedra, corners with six OErMn3 trigonal pyramids, and edges with three equivalent OEr3Mn tetrahedra. In the second O2- site, O2- is bonded to one Er3+ and three equivalent Mn3+ atoms to form OErMn3 trigonal pyramids that share corners with six equivalent OEr3Mn tetrahedra, corners with six equivalent OErMn3 trigonal pyramids, and edges with three equivalent OEr3Mn tetrahedra. In the third O2- site, O2- is bonded to three Er3+ and one Mn3+ atom to form distorted OEr3Mn tetrahedra that share corners with ten OEr3Mn tetrahedra, corners with four equivalent OErMn3 trigonal pyramids, edges with three equivalent OEr3Mn tetrahedra, and an edgeedge with one OErMn3 trigonal pyramid. In the fourth O2- site, O2- is bonded to three Er3+ and one Mn3+ atom to form OEr3Mn tetrahedra that share corners with ten OEr3Mn tetrahedra, corners with two equivalent OErMn3 trigonal pyramids, edges with three equivalent OEr3Mn tetrahedra, and edges with two equivalent OErMn3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErMnO3 by Materials Project

ErMnO3 is Orthorhombic Perovskite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Er3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Er–O bond distances ranging from 2.23–2.62 Å. Mn3+ is bonded to six O2- atoms to form corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 38–42°. There are a spread of Mn–O bond distances ranging from 1.94–2.22 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Er3+ and two equivalent Mn3+ atoms. In the second O2- site, O2- is bonded to two equivalent Er3+ and two equivalent Mn3+ atoms to form distorted corner-sharing OEr2Mn2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Intrinsic and extrinsic conduction contributions at nominally neutral domain walls in hexagonal manganites

Conductive and electrostatic atomic force microscopy (cAFM and EFM) are used to investigate the electric conduction at nominally neutral domain walls in hexagonal manganites. The EFM measurements reveal a propensity of mobile charge carriers to accumulate at the nominally neutral domain walls in ErMnO3, which is corroborated by cAFM scans showing locally enhanced direct current conductance. Our findings are explained based on the established segregation enthalpy profiles for oxygen vacancies and interstitials, providing a microscopic model for previous, seemingly disconnected observations ranging from insulating to conducting behavior. In addition, we observe variations in conductance between different nominally neutral walls that we attribute to deviations from the ideal charge-neutral structure within the bulk, leading to a superposition of extrinsic and intrinsic contributions. Our study clarifies the complex transport properties at nominally neutral domain walls in hexagonal manganites and establishes the possibility to tune their electronic response based on oxidation conditions, opening the door for domain-wall-based sensor technology.

Schultheiß, J. (ORCID:0000000173891295)↗
DOE OSTI2022

The Third Dimension of Ferroelectric Domain Walls

Abstract Ferroelectric domain walls are quasi‐2D systems that show great promise for the development of nonvolatile memory, memristor technology, and electronic components with ultrasmall feature size. Electric fields, for example, can change the domain wall orientation relative to the spontaneous polarization and switch between resistive and conductive states, controlling the electrical current. Being embedded in a 3D material, however, the domain walls are not perfectly flat and can form networks, which leads to complex physical structures. In this work, the importance of the nanoscale structure for the emergent transport properties is demonstrated, studying electronic conduction in the 3D network of neutral and charged domain walls in ErMnO 3 . By combining tomographic microscopy techniques and finite element modeling, the contribution of domain walls within the bulk is clarified and the significance of curvature effects for the local conduction is shown down to the nanoscale. The findings provide insights into the propagation of electrical currents in domain wall networks, reveal additional degrees of freedom for their control, and provide quantitative guidelines for the design of domain‐wall‐based technology.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Magnetoelastic properties of multiferroic hexagonal ErMnO 3

Here, the strength and dynamics of magnetoelastic coupling through the paramagnetic (PM) – antiferromagnetic (AFM) – ferrimagnetic (FIM) transitions in multiferroic hexagonal ErMnO 3 have been investigated by Resonant Ultrasound Spectroscopy. Elastic stiffening by up to 2% below the PM – AFM transition at 80 K arises from biquadratic coupling between strain and the magnetic order parameter with relaxation times longer than ~10 -6 s for the response of spins to changes in strain. In contrast with YMnO 3 , the PM – AFM transition in ErMnO 3 is accompanied by a peak in acoustic loss immediately below the Néel point which is interpreted in terms of strain relaxation accompanying ordering of spins of Er 3+ at 4b sites. Changes in the magnetic ordering scheme at the AFM – FIM transition near 3 K are accompanied by elastic softening of ~0.03 %. During poling of the low temperature ferrimagnetic structure round magnetic hysteresis loops, small changes in elastic stiffness which arise due to the contribution of piezomagnetic and/or piezoelectric moduli are detected. Contributions of piezoelectric moduli to acoustic resonance frequencies also permit changes in the configuration of ferroelectric domains to be detected in response both to cycling through this transition and to application of a magnetic field. A peak in acoustic loss in the vicinity of 250 K is attributed to strain-mediated pinning/freezing of some aspect of the domain microstructure with an activation energy of ~0.25–0.3 eV. A return to the original elastic properties on heating to temperatures above ~250 K is interpreted in terms of backswitching of domains to the configuration they had at the start. These observations confirm the existence of subtle variations in magnetoelastic coupling behaviour relating to both the magnetic order parameters and magnetic domain structures.

36 MATERIALS SCIENCE↗